The present invention relates to the field of power electronics and in particular to a circuit having an active element, a drive circuit, a control logic and an interface circuit, as well as to a system comprising one or several such circuits.
Frequently, modern power electronic systems include a plurality of power electronic elements that are to be actively controlled, for example switches in the form of IGBTs or MOSFETs. Examples for such power electronic systems can be found in on-board chargers for electronic vehicles, in multiport DC/DC converters for complex energy management tasks or also in converters for RPM-regulated control of electric machines. Realizing such power electronic systems is frequently performed by dividing the system into partial or subsystems, such as into an active front end circuit and a galvanically isolated converter stage in the case of an on-board charger, into several bidirectional boost/buck choppers in the case of multiport DC/DC converters or into several half bridge circuits in motor inverters. Further power electronic systems having a plurality of actively controllable power electronic elements include, for example, inverters for converting direct current generated by solar plants into an alternating current for feeding into an alternating current network.
In the case of power electronic switches, energy, for example in the form of an auxiliary energy signal for supplying the control circuit, and the actual switch control signal are necessitated, for example a gate control signal in the case of realizing the switch by using, for example, IGBTs or field effect transistors. Here, it is necessitated to possibly control a great plurality of active power switches or active power elements in an interference-proof manner and to simultaneously minimize the effort. Further, galvanic isolation between the higher-level control unit facing the user and the actual power electronic unit, e.g. the power module, can be provided or necessitated.
Galvanically isolated drive or control circuits are known in conventional technology. The effort for galvanically isolated control of several power switches is significant. Thus, known approaches also use so-called intelligent power modules (IPM), for example designed for realizing complete sub units, for example in the form of a motor inverter including a braking chopper. These approaches are characterized by extending a typical power module by integrating further functionalities, for example by integrating the drive or control circuit, wherein the common feature of all intelligent power modules can be seen in the fact that a higher-level control unit comprising the necessitated control logic is necessitated, for example for providing respective gate control signals to the IPM.
Further, in conventional technology, approaches are known aiming at reducing the great interface effort for controlling the individual power electronic switches, e.g. the IPM, or the necessitated circuits for providing the necessitated auxiliary supplies. As an example, reference is made to the thesis of S. Zeltner “Untersuchungen zu isolierenden verlustarmen kompakten Ansteuerschaltungen mit integrierter Regelung des Laststroms” (“Analysis concerning isolating low-loss compact control circuits with integrated regulation of the load current”), University of Erlangen, 2011. The concept described therein expands the functionality of a control circuit by regulator units and units for generating the gate control signals, such that this drive or control circuit fulfills the functionality of a controlled current source. Thereby, the interface effort can be reduced, since it is now only necessitated to transfer the auxiliary supply voltages as well as the trigger and set value specifications to the IPM. In this concept, the units for expanding the functionality, the regulator and the PWM unit are on the primary side of the control circuit (i.e., the same are directly connected to the higher-level control unit), which, however, necessitates further measures with respect to signal transmission. Thus, e.g., for interference-proof transmission of a synchronization signal and for transmission of a set value specification, for example, digital transmission or the usage of differential signal transmissions or further galvanic isolations are necessitated. This results in a significant interface effort. Additionally, it is disadvantageous that energy transmission is performed isolated from the gate signal transmission, such that the overall coupling capacitance between the higher-level control unit and the secondary side facing the power electronics is increased.
Further, approaches are known in conventional technology for minimizing the effort in the context of necessitated galvanic isolation and gate signal transmission by transmitting the gate control signal as well as the necessitated auxiliary energy via a common transformer, such as described, for example, by S. Y. Hui in “Coreless Printed Circuit Board (PCB) Transformers for Power MOSFET/IGBT Gate Drive Circuits”, IEEE Transactions on Power Electronics, Vol. 14, No. 3, May 1999 or by S. Zeltner et al., “A Compact IGBT Driver for High Temperature Applications”, PCIM Europe 2003, Nuremberg 2003, Germany. This results in a reduction of the overall coupling capacitance between primary side and secondary side, however, it is disadvantageous that there are tradeoffs with respect to the power to be transmitted on the one side and the obtainable transmission characteristics of the gate control signal on the other side. For example, the gate control signal can be provided with an undesired delay or an undesired jitter, such that exact and proper control is not possible, in particular not with increasing switching frequencies in power electronic systems, such as can be found when using modern power electronic circuits in SiC or GaN technology. There, this problem increasingly manifests itself and is more and more difficult to solve.
Further, in conventional technology, an approach according to U.S. Pat. No. 5,900,683 by Ford is known, which discloses an isolated gate driver for power circuit elements, where it is intended to control a gate driver by using a first load signal modulated at a first frequency and by using a second load signal modulated at a second frequency, wherein the two frequencies differ from one another and are selected such that the first load signal effects switching on of the transistor and the second load signal effects switching off of the transistor. The disadvantage of this procedure is similar to the disadvantages described above in the context of the approaches of Hui et al and S. Zeltner et al., namely that transmitting the control signals from external sources (typically a central control unit) is performed via and isolation barrier to the switches, such that the above-described problems with respect to interferences of the signals during transmission, in particular with increasing switching frequencies, occur.
Again another approach is described in US 2012/0212075 A1 by Arnet, where a programmable gate controller circuit is provided including at least one programmable gate controller connected to a central controller via a bidirectional connection and to at least one power switch. The control signals are generated in the programmable gate controller and are provided to the switch, wherein the gate controller is programmed by control signals from the central controller. The bidirectional communication takes place via a bidirectional bus, wherein isolation between the central controller and the programmable gate controller is provided. It is a disadvantage of this procedure that the necessitated auxiliary energy signals are provided by additional external sources, such that further galvanically decoupled interfaces are provided for the auxiliary energy supplies (e.g. for gate drivers, logic units, measurement circuits).